The subject matter herein relates generally to systems and methods for separating immiscible liquids and, more specifically, to systems and methods that effectively isolate at least one of the liquids so that the liquid(s) may be analyzed and/or used in an assay.
Various protocols in biological or chemical analysis involve performing a large number of controlled reactions. The designated reactions may be performed to prepare and/or analyze a biological substance. Digital fluidics (DF) is one technology that may be used to perform such reactions. In DF technology, aqueous droplets may be moved or manipulated (e.g., combined or divided) using electrowetting-mediated operations. For example, a DF device may include a cartridge having an enclosed cavity that is defined by one or more substrates. An array of electrodes may be arranged along the substrate(s) and positioned adjacent to the cavity. The cavity may be filled with a filler liquid (e.g., oil) that is immiscible with respect to the aqueous droplets. The electrodes are configured to provide different electric fields in accordance with a predetermined sequence or schedule to transport, mix, filter, monitor, and/or analyze the aqueous droplets within the DF device. The predetermined sequence may subject the aqueous droplets to designated reactions in order to, for example, prepare a biological substance.
Complex steps may be implemented to control the aqueous droplets and prepare the desired biological substance. As one example, DF technology may be used to prepare libraries of fragmented nucleic acids for next generation sequencing (NGS). After conducting the designated reactions, the droplets may be transported to different locations within the DF device that are accessible to the user. The user may remove each droplet by, for example, inserting a pipettor into the cavity and withdrawing a small volume (e.g., 20 μl) that includes both the aqueous solution and the filler liquid. Often, the aqueous solution is a fraction of the entire liquid with the filler liquid forming a majority of the liquid. For example, a volume of the filler liquid may be two time (2×), ten times (10×), or twenty times (20×) the volume of the aqueous solution.
For some applications, it may be necessary to separate the aqueous solution from the filler liquid so that the aqueous solution may be used in an assay or may be recovered at the end of an assay or workflow. Separating small volumes of liquid from other liquids in a reliable and efficient manner, however, can be challenging. One conventional method for separating a liquid mixture that includes an aqueous solution and a filler liquid includes depositing the mixture into a well and spinning the well in a centrifuge to separate the liquids into different layers. The layer of the filler liquid may form on top of the layer of the aqueous solution. The layer of the filler liquid may be removed with a pipettor or through decanting. For particular protocols, this separation process may take 45 minutes or longer. Moreover, the process can be messy and unpredictable, especially when working with several different samples.
Accordingly, there is a need for a method of separating two or more immiscible liquids in a manner that is at least one of quicker, more efficient, or more reliable than known separation processes.